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PubMed1995

Modifications of the hydrophilicity of heterocyclic methacrylate copolymers for protein release.

A series of copolymers comprising ethyl methacrylate (EM) and tetrahydrofurfuryl methacrylate (THFMA) gelled with either THFMA monomer or hydroxyethyl methacrylate (HEMA) monomer have been developed. In this paper, we examine the water uptake characteristics of the polymer systems and address the possibility of increasing the hydrophilicity of the systems by changing the ratios of the copolymers. We have investigated whether protein release from the polymers is related to the composition of the polymer systems. More protein was released from the polymers gelled with the more hydrophilic monomer (HEMA) than with THFMA. This was consistent with the calculated diffusion coefficients, which were 10 times greater for the polymers gelled with HEMA than those gelled with THFMA. Interestingly, the water uptake and protein release profiles were not dependent on the ratio of EM and THFMA in the copolymers. This is probably due to the conflicting roles of THFMA in the copolymer; it is both the more hydrophilic component as well as a cross-linking agent. In addition, it would appear that the structural and surface topography of these polymers had more significant effects on protein release than copolymer composition.

Absorption↗

PubMed1987

Aquatic toxicity of acrylates and methacrylates: quantitative structure-activity relationships based on Kow and LC50.

Recent EPA scrutiny of acrylate and methacrylate monomers has resulted in restrictive consent orders and Significant New Use Rules under the Toxic Substances Control Act, based on structure-activity relationships using mouse skin painting studies. The concern is centered on human health issues regarding worker and consumer exposure. Environmental issues, such as aquatic toxicity, are still of concern. Understanding the relationships and environmental risks to aquatic organisms may improve the understanding of the potential risks to human health. This study evaluates the quantitative structure-activity relationships from measured log Kow's and log LC50's for Pimephales promelas (fathead minnow) and Carassius auratus (goldfish). Scientific support of the current regulations is also addressed. Two monomer classes were designated: acrylates and methacrylates. Spearman rank correlation and linear regression were run. Based on this study, an ecotoxicological difference exists between acrylates and methacrylates. Regulatory activities and scientific study should reflect this difference.

Acrylates↗

PubMed2005

Fabrication of DNA microarrays onto poly(methyl methacrylate) with ultraviolet patterning and microfluidics for the detection of low-abundant point mutations.

We have developed a simple ultraviolet (UV)-photomodification protocol using poly(methyl methacrylate) and polycarbonate to produce functional scaffolds consisting of carboxylic groups that allow covalent attachment of amine-terminated oligonucleotide probes to these surface groups through carbodiimide coupling. Use of the photomodification procedure coupled to microfluidics allowed for the rapid generation of medium-density DNA microarrays. The method reported herein involves the use of poly(dimethylsiloxane) microchannels reversibly sealed to photomodified poly(methyl methacrylate) surfaces to serve as stencils for patterning the oligonucleotide probes. After array construction, the poly(dimethylsiloxane) stencil is rotated 90 degrees to allow interrogation of the array using microfluidics. The photomodification process for array fabrication involves only three steps: (1) broadband UV exposure of the polymer surface, (2) carbodiimide coupling of amine-terminated oligonucleotide probes to the surface (via an amide bond), and (3) washing of the surface. The density of probes attached to this activated surface was found to be approximately 41pmolcm(-2), near the steric-saturation limit for short oligonucleotide probes. We demonstrate the use of this procedure for screening multiple KRAS2 mutations possessing high diagnostic value for colorectal cancers. A ligase detection reaction/universal array assay was carried out using parallel detection of two different low-abundant DNA point mutations in KRAS2 oncogenes with the allelic composition evaluated at one locus. Four zip code probes immobilized onto the poly(methyl methacrylate) surface directed allele-specific ligation products containing mutations in the KRAS2 gene (12.2D, 12.2A, 12.2V, and 13.4D) to the appropriate address of a universal array with minimal amounts of cross-hybridization or misligation.

Adsorption↗

PubMed2005

Shear bond strength of experimental methacrylated beta-cyclodextrin-based formulations.

Previous studies have shown that methacrylated beta-cyclodextrins (MCDs) can be used as comonomers in resin-based dental composites. These MCDs by virtue of having several polymerizable methacrylate groups and hydrophilic hydroxyl groups, may also promote bonding of dental composites to dentin. This study evaluated MCDs as adhesive comonomers, and optimized comonomer and polymerization initiator concentrations for maximum shear bond strength (SBS). Experimental MCD-based bonding formulations in acetone were prepared by mixing 33 mass fraction % MCDs with (10, 20, 30, 40, or 50) mass fraction % of 2-hydroxyethyl methacrylate (HEMA). The MCD/HEMA-based solutions were activated with varied amounts of camphorquinone (CQ) and ethyl 4-dimethylamino benzoate (4E). Samples for SBS were prepared by bonding a composite resin to acid-etched dentin surfaces of extracted human molars with the experimental bonding solutions. The specimens were immersed in 37 degrees C water for 24 h and bond strengths were determined in shear mode. With increasing HEMA concentration, the SBS values of MCD-bonding solutions increased to 16 MPa at a composition of 33% MCD, 30% HEMA, and 37% acetone by mass. Also, SBS values of MCD-bonding solutions varied as a function of the CQ and 4E concentrations and passed through a maximum SBS at 21 MPa, which was comparable to that of a commercial control. This preliminary study indicated that nonacidic MCD monomers could be used as an adhesion-promoting comonomer. Additional modification of MCDs having both polymerizable groups and anionic ligand groups, e.g., polymerizable acidic cyclodextrin derivatives should increase the SBS even further.

Adhesiveness↗

PubMed2005

Preparation of low flow-resistant methacrylate-based monolithic stationary phases of different hydrophobicity and the application to rapid reversed-phase liquid chromatographic separation of alkylbenzenes at high flow rate and elevated temperature.

Low flow-resistant alkyl methacrylate-based monolithic stationary phases of different hydrophobicity were constructed for reversed-phase capillary liquid chromatography by thermally initiated radical polymerization of respective methacrylate ester monomer with different alkyl chain (C2, C4, C6, C12, C18) and ethylene glycol dimethacrylate (EDMA) in a 250 microm i.d. fused silica capillary. The hydrophobicity was basically controlled by changing the length and/or the density of the alkyl-chain, while the composition and the ratio of porogenic solvent were adjusted to obtain highly permeable rigid monoliths with adequate column efficiency. Among the prepared monolithic stationary phases, C18-methacrylate monoliths polymerized from a binary porogenic solvent of isoamyl alcohol and 1,4-buthandiol exhibited the most promising performance in terms of hydraulic resistance and column efficiency. The pressure drops of 20-cm long monolithic columns were below approximately 0.4 MPa at a normal linear velocity of 1mm/s (a flow rate of 3 microL/min), and the numbers of theoretical plates for alkylbenzenes mostly exceeded 3000 plates/20 cm. The produced monolithic columns had good mechanical strength for high pressure and temperature, and could be properly operated even at a temperature of 80 degrees C and at a pressure of at least 33 MPa. At 80 degrees C, the theoretical plate numbers reached 6000 plates/20 cm because of the enhanced mass transfer. Due to the novel hydraulic resistance and mechanical strength, the separation time could be reduced 120-fold simply by raising the flow rate and column temperature.

Benzene↗

PubMed2005

Degree of conversion and flexural properties of a dendrimer/methyl methacrylate copolymer: design of experiments and statistical screening.

OBJECTIVES: The aim of this study was to investigate the effect of photosensitive initiator and activator concentrations on the degree of conversion and flexural properties of an experimental photopolymerized dental copolymer containing dendrimer. METHODS: The experimental resin system consisted of a dendrimer with 12 methacrylate groups and methyl methacrylate in a mass ratio of 80:20. The initiator and activator used were camphorquinone and 2-(N,N-dimethylamino)ethyl methacrylate, whose concentrations varied individually from 1 to 4 wt%. The degree of conversion was determined with FTIR spectroscopy, and flexural strength and flexural modulus with the three-point bending test. The experiments were designed and analyzed, and the results plotted with Modde 5.0 software. RESULTS: The highest degree of conversion was obtained with 2.5 wt% initiator and activator concentrations, the highest flexural strength with 2.5 wt% initiator and 1.0 wt% activator concentration, and the highest flexural modulus with 1.0 wt% initiator and activator concentrations. SIGNIFICANCE: The results indicated that the degree of conversion increased, and flexural strength and flexural modulus decreased, with increasing initiator and activator concentrations. The high concentrations of initiator probably inhibited the transmittance of the active wavelengths to the depths of the samples (the inner filter effect), resulting in inhomogeneous conversion and thus decreased mechanical properties.

Elasticity↗

PubMed2006

pH-responsive polymeric micelles of poly(ethylene glycol)-b-poly(alkyl(meth)acrylate-co-methacrylic acid): influence of the copolymer composition on self-assembling properties and release of candesartan cilexetil.

The objective of the present study was to investigate the influence of chemical structure and molecular weight of pH-sensitive block copolymers on their self-assembling properties, the loading and the release of candesartan cilexetil (CDN). Block copolymers of poly(ethylene glycol) and t-butyl methacrylate, iso-butyl acrylate, n-butyl acrylate or propyl methacrylate were synthesized by atom transfer radical polymerization. pH-sensitivity was obtained by hydrolysis of t-butyl groups. The poorly water-soluble drug CDN was incorporated in the micelles and the in vitro drug release was evaluated as a function of pH. The critical aggregation concentration of hydrolyzed copolymers (pK(a)=6.2-6.6) was higher compared to the unhydrolyzed ones. Dynamic light scattering studies and atomic force microscopy images revealed uniform size micelles with aggregation numbers ranging from 60 to 160. The entrapment efficiency of CDN was generally found to be above 90%, with drug loading levels reaching approximately 20% (w/w). Differential scanning calorimetry studies showed the amorphous nature of entrapped CDN. The release of CDN from pH-sensitive micelles was triggered upon an increase in pH from 1.2 to 7.2. These findings suggest that the PEG-b-poly(alkyl(meth)acrylate-co-methacrylic acid)s can self-assemble to form micelles which exhibit high loading capacities for CDN and release the drug in a pH-dependent fashion.

Angiotensin II Type 1 Receptor Blockers↗

PubMed2006

Preparation and characterization of long alkyl chain methacrylate-based monolithic column for capillary chromatography.

This paper describes the fabrication of long alkyl chain methacrylate monolithic materials for using as stationary phases in capillary liquid chromatography. Following deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (gamma-MAPS), monoliths were formed by co-polymerisation of stearyl methacrylate (SMA) with ethylene glycol dimethacrylate (EDMA) in the presence of the initiator AIBN and a mixture of porogens including iso-amyl alcohol and 1,4-butanediol. The monoliths were prepared in 100 microm i.d. capillaries and the composition of the polymerisation mixtures were optimised in terms of the ratio of SMA/EDMA, the porogen composition and ratio of porogen to monomers. As the porogen weight fraction decreased, the microglobules became smaller and as expected, the total porosity decreased. In order to determine the usability of such materials, the column permeability K was measured by pumping water through the columns at different linear flow rates. Good results were obtained when these capillaries were used to separate mixtures of weak acids, neutral and basic compounds.

Chromatography, High Pressure Liquid↗

PubMed2005

Surface modification of silica nanoparticles by UV-induced graft polymerization of methyl methacrylate.

In this study we modified the surface of silica nanoparticles with methyl methacrylate by UV-induced graft polymerization. It is a surface-initiated polymerization reaction induced by ultraviolet irradiation. The resulting organic-inorganic nanocomposites were near-monodisperse and fabricated without homopolymerization of the monomer. Substantial increase in mean particle size was observed by SEM image analysis after UV-induced grafting of methyl methacrylate onto pure silica particles. FT-Raman spectroscopy and X-ray photoelectron spectroscopy studies of these materials revealed the successful grafting of methyl methacrylate onto the silica surface. The formation of a covalent bond between the grafted PMMA chains and silica surface was indicated by FT-Raman spectra. Thermogravimetric analysis of the PMMA-grafted silica particles indicated the polymer contents in good agreement with SEM photographs.

Nanoparticles↗

PubMed2006

Bondability of Resilon to a methacrylate-based root canal sealer.

Resilon broadens the dimensions of endodontic adhesion by introducing the possibility of creating monoblocs between root canal filling materials and intraradicular dentin by using methacrylate-based sealers. The adhesive strength of Resilon to RealSeal, a methacrylate-based root canal sealer, was evaluated using a modified microshear bond testing design. Flat Resilon surfaces with different roughness were created for bonding to the sealer and compared to a composite control. The composite control exhibited mean shear strength 7.3 to 26.9 times higher than those of the Resilon groups. Shear strength differences among the Resilon groups of different surface roughness highlighted the contribution of micromechanical versus chemical coupling in sealer retention. Ultrastructural evidence of phase separation of polymeric components in Resilon suggested that the amount of dimethacrylate incorporated into this filled, thermoplastic composite may not yet be optimized for effective chemical coupling to methacrylate-based sealers.

Dental Bonding↗

PubMed2001

The effect of two hydrophilic monomers on the water uptake of a heterocyclic methacrylate system.

The room temperature polymerising system poly(ethyl methacrylate) (PEM)/tetrahydrofurfuryl methcrylate (THFM) has been modified by replacing some of the THFM by hydroxyethyl methacrylate (HEMA) and hydroxypropyl methacrylate (HPM), respectively. In both cases, the equilibrium uptake of the parent system is reduced substantially, in spite of the hydrophilic nature of these monomers. The effect is less with HPM. Corresponding to these decreases in uptake are substantial increases in the diffusion coefficients. This points to changes from a cluster-dominated process, to a more continuum-based process in the dual monomer systems. Addition of chicken serum albumin to these systems increases water uptake. At higher levels of HEMA addition, there is a substantial increase in polymerisation exotherm.

Absorption↗

PubMed2001

Polypropylene fumarate/phloroglucinol triglycidyl methacrylate blend for use as partially biodegradable orthopaedic cement.

Polypropylene fumarate/phloroglucinol triglycidyl methacrylate oligomeric blend-based bone cement was studied. Higher the percentage of phloroglucinol triglycidyl methacrylate, lesser the setting time. An optimum setting time could be arrived with 50:50 blend composition of the two oligomers. Composite cement of 50:50 blend prepared with hydroxyapatite granules of particle size 125 microm binds bovine rib bones. The tensile strength of this adhesive bond was found to be 1.11 kPa. The thermal studies suggest the onset of cross-linking reaction in the cured blend if the blend is heated. The absence of softening endotherm in the cured blend shows the thermosetting-like amorphous nature of blend system, which may restrict the changes in creep properties. The in vitro biodegradation studies reveal possible association of calcium ions with negatively charged units of degrading polymer chain resulting in slow down of degradation. Relatively slow degradation was observed in Ringer's solution. The study reveals the potential use of polypropylene fumarate/phloroglucinol triglycidyl methacrylate as partially degradable polymeric cement for orthopaedic applications.

Animals↗

PubMed1998

Fluoride ion release from two methacrylate polymer systems.

The release of fluoride ions from two room-temperature polymerising systems containing sodium and potassium fluoride, respectively, has been studied. The polymer systems comprised poly(ethyl methacrylate) powder (PEM), with tetrahydrofurfuryl methacrylate (THFM), and n-butyl methacrylate (nBM), respectively. The water uptake of these systems was drastically increased by the presence of fluorides, the increase being much higher with the PEM/THFM system. In both cases, uptake was a monotonic function of the molarity of the fluoride added. The uptake process was in general non-Fickian. However, for all systems, the fluoride release process was Fickian, and diffusion coefficients could be calculated. The amount of fluoride released, and the diffusion coefficients obtained, appeared unrelated to the extent of water uptake of the parent polymers.

Absorption↗

PubMed1999

The modulation of corneal keratocyte and epithelial cell responses to poly(2-hydroxyethyl methacrylate) hydrogel surfaces: phosphorylation decreases collagenase production in vitro.

We examined the regulation of collagenase production by rabbit keratocyte, epithelial and mixed keratocyte/epithelial cell cultures which were exposed to poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel surfaces with different chemistries and morphologies (sponge and homogeneous gels). Tissue culture modified polystyrene (TCP), used as a control surface, induced the maximum collagenase response with all cell culture types. Copolymer homogeneous gels containing 2-ethoxyethyl methacrylate (EEMA) or methyl methacrylate (MMA) induced a high response in keratocyte cultures, whilst PHEMA hydrogels induced a moderate response and the phosphorylated PHEMA (phos-PHEMA) hydrogel induced no response. Epithelial cells cultured on PHEMA, copolymer and phos-PHEMA hydrogels produced less collagenase activity than the keratocyte cells. The profile of collagenases produced by epithelial cells in response to phos-PHEMA was different to that for the other hydrogels. Co-cultured cells produced higher levels of collagenase (relative to the TCP) in response to hydrogels than did either the keratocytes or epithelial cells alone, but the response of phos-PHEMA was still the lowest. The overall enzyme response to the sponge hydrogels was lower than that to the homogeneous hydrogels, although this effect was less prominent in the keratocyte cultures. The markedly reduced and alternative collagenase responses to phosphorylated surfaces was not a consequence of cell death, and may be a phenomenon related to changes in cell surface charge and morphology.

Animals↗

PubMed2001

NSAIDs bound to methacrylic carriers: microstructural characterization and in vitro release analysis.

Chemically controlled drug delivery systems or 'polymeric drugs' based on copolymers of 2-hydroxyethyl methacrylate, HEMA, and five methacrylic derivatives which incorporate ibuprofen or ketoprofen in their chemical structure by means of labile ester bonds, MAI, MAK, MAEK, MEI and MEK, have been prepared by free radical polymerization in solution at 50 degrees C. Three different spacers have been incorporated to the monomer structure: an aromatic amide, an aliphatic ester and a combined aromatic amide/aliphatic ester. Copolymerization reactions of the methacrylamide derivatives with HEMA follow the terminal model with reactivity ratio values, determined by the Tidwell and Mortimer (J. Polym. Sci. A 1965;3:369-378) non-linear least-squares treatment, of r(MAI)=0.38, r(HEMA)=1.69; r(MAK)=0.30, r(HEMA)=0.48; and r(MAEK)=0.66, r(HEMA)=2.85. From these values and considering that the methacrylates MEI and MEK are structurally related to HEMA, the microstructural analysis give us a random distribution of the monomeric units. The HEMA-rich copolymers, used for the in vitro experiments, showed a very high population of sequences with the active residue isolated by HEMA units. The in vitro release experiments were carried out at pH 7.4 and 9, using six different compositions for each copolymer system (1, 2.5, 5, 10, 20 and 30 wt% of the active acrylic monomer). The results show a controlled release in terms of weeks with very different profiles which depend on the type of spacer (the aromatic ester is more susceptible to hydrolysis than the aliphatic one), drug (ketoprofen release rate is higher than the ibuprofen one), composition of the copolymer (as a general rule, the release rate increases with the content of the attached drug until some composition where this effect is reverted because of the global increase in hydrophobicity) and pH (the release rate is noticeably higher in a strong basic medium, pH 9).

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1998

2-(Dimethylamino)ethyl methacrylate based (co)polymers as gene transfer agents.

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is a water-soluble cationic polymer, which is able to bind to DNA by electrostatic interactions. At a polymer/plasmid ratio above 2 (w/w) positively charged complexes were formed with a size around 0.2 microm. The transfection efficiency of polymer/plasmid complexes was evaluated in cell culture (COS-7 and OVCAR-3 cells) using a pCMV-lacZ plasmid, encoding for beta-galactosidase, as a reporter gene. The optimal transfection efficiency was found at a PDMAEMA/plasmid ratio of 3-5 (w/w). Under these conditions 3-6% of the cells were actually transfected. Like other cationic polymers, PDMAEMA is slightly cytotoxic. This activity was partially masked by complexing the polymer with DNA. A pronounced effect of the molecular weight of the polymer on the transfection efficiency was observed. An increasing molecular weight resulted in an increasing number of transfected cells. Dynamic light scattering experiments showed that high molecular weight polymers (Mw>300 kDa) were able to condense DNA effectively (particle size 0.15-0.20 microm). In contrast, when plasmid was incubated with low molecular weight PDMAEMA, large complexes were formed (size 0.5-1.0 microm). Copolymers of DMAEMA with methyl methacrylate (MMA), ethoxytriethylene glycol methacrylate (triEGMA) or N-vinyl-pyrrolidone (NVP) also acted as transfection agents. A copolymer with 20 mol % of MMA showed a reduced transfection efficiency and a substantial increased cytotoxicity compared with a homopolymer of the same molecular weight. A copolymer with triEGMA (48 mol %) showed both a reduced transfection efficiency and a reduced cytotoxicity, whereas a copolymer with NVP (54 mol %) showed an increased transfection efficiency and a decreased cytotoxicity as compared to a DMAEMA homopolymer.

Animals↗

PubMed1998

Bonding efficacy and interfacial microstructure between resin and dentine primed with glyceryl methacrylate.

OBJECTIVES: To evaluate the effect of two experimental primers based on glyceryl methacrylate (GM, 2,3-dihydroxypropyl methacrylate) and 2-hydroxyethyl methacrylate (2-HEMA) on the marginal adaptation of light-cured composite placed into cylindrical dentine cavities and to study the interfacial microstructure. METHODS: The bonding efficacy of two experimental dentine primers combined with a dentine cleanser composed of either 0.5 mol l-1 EDTA neutralized to pH 7.4 by sodium hydroxide or 10% citric acid containing 3% ferric chloride (10-3 solution), and a commercial dentine bonding agent containing phosphate ester, were examined by measuring the wall-to-wall polymerization contraction gap of a commercial light-activated resin composite placed into cylindrical dentine cavities. The adhesive interface between the dentine and the dentine adhesive was observed using a transmission electron microscope (TEM). RESULTS: The formation of a contraction gap was completely prevented by priming with GM, regardless of the dentine cleanser used. However, in groups primed with 2-HEMA, gap formation was observed in three and four specimens out of 10 in the groups that were cleaned with the EDTA and 10-3 solution, respectively. In samples primed with GM, a high-density layer was observed by TEM at the superficial dentine in the hybrid layer, which may have indicated a high monomer content, whereas no density variations were observed in the hybrid layer in samples primed with 2-HEMA.

Adhesives↗

PubMed1999

Experimental neodymium:YAG laser damage to acrylic, poly(methyl methacrylate), and silicone intraocular lens materials.

PURPOSE: To compare neodymium:YAG (Nd:YAG) laser effects on acrylic, silicone, and poly(methyl methacrylate) (PMMA) intraocular lens (IOL) polymers. METHODS: Ten Nd:YAG laser exposures were produced in each of 6 implantation-quality acrylic (Alcon MA60BM), silicone (Staar AQ1016), and PMMA (Alcon MC60BM) IOLs under identical conditions. Each polymer type was irradiated at 6 power settings (0.3, 0.5, 1.0, 1.5, 2.0, and 3.0 mJ) and at 2 focal points (midpoint of lens optic and on the posterior surface to which a cellophane membrane was affixed). The linear extent of the damage was measured using light microscopy. Specimens exposed to 1.0 mJ were processed for scanning electron microscopy. RESULTS: The damage threshold (> or = 5 microns depth) was 0.3 mJ for silicone and 1.0 mJ for acrylic and PMMA IOLs. At the clinically relevant power levels, 1.0 to 2.0 mJ, the depth of damage in the acrylic polymer was 11.9 to 30.5 times less than the depth in the silicone polymer. Similarly, the depth of damage in the PMMA polymer was 5.4 to 52.6 times less than the depth in the silicone polymer. The morphologic pattern of damage in the silicone IOL showed a deep, irregularly configured trough with meandering tendrils. Acrylic IOL damage morphology consisted of an ameboid-shaped entry site without radiating fractures and mild posterior penetration. Poly(methyl methacrylate) IOL damage consisted of a shallow focal trough with radiating fractures. CONCLUSIONS: The silicone IOL polymer had the lowest threshold for laser-induced damage and greater linear extension of damage than the PMMA and acrylic IOL polymers. Poly(methyl methacrylate) and silicone polymers exhibited collateral damage or ejected particulates adjacent to the entry site, whereas the acrylic polymer showed a discrete locus of damage.

Acrylic Resins↗